Abstract
Background Drug-resistant epilepsy is a common, disabling, and life-threatening disease. Vagus nerve stimulation (VNS) is a valuable tool in its treatment. Cyclic patterns in seizures have recently gained considerable attention, in particular the idea of using these cycles to tailor neurostimulation therapies. Modern VNS devices detect and respond to rises in heart rate, yet there has been minimal investigation into the presence of cycles in heart rate detections in VNS.
Methods Tachycardia detection data from SenTiva M1000 and Aspire M106 VNS devices were analysed in 42 consecutive outpatients. One patient was excluded due to insufficient data. Cycles in tachycardia detections were identified using spectral analysis from both hourly and daily detection counts.
Results Cycles in tachycardia detections were present in almost all subjects (39/41). Circadian (24hr) rhythm was the most common cycle, present in 86.8% of subjects with hourly detection counts recorded (33/38). Other common ultradian (<24 hour) cycles were 12 hours and 8 hours, present in 44.7% (17/38) and 28.9% (11/38) of subjects, respectively. Multi-day (infradian) cycles were identified in 26/29 subjects with analysable daily counts (89.7%). These cycle lengths were variable, but the most common were: approximately monthly (24 - 32 days) (48.2%, 14/29), weekly (6–8 days) (27.6%, 8/29), and bi-monthly (58 - 60 days) (20.7%, 6/29).
Conclusion We show for the first time that multi-day cycles in tachycardia detections can be demonstrated using standard implantable VNS systems. The pattern of these cycles could potentially be used to provide better tailored epilepsy treatment and VNS programming.
